Bridgeport Lake Private Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Bridgeport Lake Private Observatory clear sky chart from 2005-11-05 to 2017-10-06.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
62%
15348
30%
47072
24%
15321
69%
15321
48%
22853

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
59%
716
24%
2506
20%
716
69%
716
40%
1220
January16th to endNight
57%
768
27%
2532
25%
768
64%
768
39%
1312
February1st to 15thNight
55%
697
28%
2181
24%
697
64%
697
41%
1120
February16th to endNight
51%
632
27%
1895
22%
632
61%
632
42%
989
March1st to 15thNight
51%
720
23%
2150
18%
720
60%
720
45%
1084
March16th to endNight
47%
768
23%
1998
13%
768
55%
768
44%
1119
April1st to 15thNight
51%
719
23%
1799
10%
719
57%
719
41%
1047
April16th to endNight
53%
720
25%
1800
11%
720
58%
720
46%
989
May1st to 15thNight
54%
578
28%
1658
19%
578
59%
578
49%
838
May16th to endNight
60%
405
26%
1528
25%
405
67%
405
39%
712
June1st to 15thNight
63%
360
28%
1440
29%
360
73%
360
45%
605
June16th to endNight
76%
360
36%
1440
41%
360
85%
360
67%
479
July1st to 15thNight
89%
340
32%
1360
42%
340
91%
340
62%
479
July16th to endNight
82%
406
36%
1444
42%
382
84%
382
49%
619
August1st to 15thNight
79%
663
35%
1737
24%
660
81%
660
67%
817
August16th to endNight
81%
764
42%
1910
26%
764
82%
764
72%
901
September1st to 15thNight
80%
720
41%
1800
27%
720
83%
720
70%
858
September16th to endNight
72%
716
43%
1962
35%
716
79%
716
64%
909
October1st to 15thNight
67%
684
33%
1989
27%
684
76%
684
55%
962
October16th to endNight
68%
704
37%
2150
34%
704
78%
704
57%
958
November1st to 15thNight
66%
700
32%
2275
30%
700
74%
700
49%
1059
November16th to endNight
57%
720
33%
2340
27%
720
68%
720
49%
1068
December1st to 15thNight
52%
720
22%
2490
17%
720
61%
720
37%
1264
December16th to endNight
47%
768
26%
2688
20%
768
59%
768
31%
1445

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
231332345%7%62%
48140
Night
1213313347%66%
47247
TransparencyDay
20%6%11%21%23%16%
47814
Night
17%6%12%24%26%13%
47073
SeeingDay
9%18%29%26%13%3
5845
Night
36%23%34%24%7%
15361

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
2233346%10%61%
1432
16th to endDay
16%233245%6%9%53%
1691
February1st to 15thDay
32442336%9%59%
1681
16th to endDay
42441446%9%55%
1579
March1st to 15thDay
3133245%7%10%55%
1809
16th to endDay
223325%5%8%10%54%
2226
April1st to 15thDay
23245%35%45%9%53%
2149
16th to endDay
1323324345%64%
2160
May1st to 15thDay
2413423347%61%
2291
16th to endDay
46%36%425%446%51%
2582
June1st to 15thDay
431432445%6%60%
2520
16th to endDay
11221322475%
2520
July1st to 15thDay
4313324445%63%
2520
16th to endDay
442432333462%
2624
August1st to 15thDay
2215%42333467%
2214
16th to endDay
231331233471%
2292
September1st to 15thDay
322342333368%
2160
16th to endDay
122212245%73%
1998
October1st to 15thDay
4322223335%66%
1765
16th to endDay
121221226%6%68%
1720
November1st to 15thDay
1213313447%65%
1584
16th to endDay
11132346%9%64%
1620
December1st to 15thDay
3224235%49%59%
1467
16th to endDay
215%5%25%6%8%10%52%
1536
January1st to 15thNight
32432445%10%59%
2506
16th to endNight
14232245%6%9%57%
2532
February1st to 15thNight
22432345%10%58%
2170
16th to endNight
42432446%8%58%
1895
March1st to 15thNight
32331246%9%62%
2150
16th to endNight
32331345%8%61%
1998
April1st to 15thNight
1313325%5%5%8%57%
1799
16th to endNight
1423323335%67%
1800
May1st to 15thNight
1212323446%67%
1658
16th to endNight
4413212345%64%
1527
June1st to 15thNight
4212213445%68%
1440
16th to endNight
11222284%
1440
July1st to 15thNight
111111246%77%
1440
16th to endNight
221222323472%
1542
August1st to 15thNight
11121122478%
1746
16th to endNight
111211135%80%
1910
September1st to 15thNight
1111222480%
1800
16th to endNight
11122223477%
1962
October1st to 15thNight
3312212335%71%
1989
16th to endNight
113212247%71%
2150
November1st to 15thNight
1212212347%70%
2275
16th to endNight
213312346%68%
2340
December1st to 15thNight
121442346%10%58%
2490
16th to endNight
125%5%245%7%11%53%
2688

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
16%9%17%29%19%7%
1432
16th to endDay
25%10%13%21%17%10%
1691
February1st to 15thDay
20%8%16%26%20%8%
1681
16th to endDay
22%8%17%26%21%2
1579
March1st to 15thDay
19%9%21%23%18%7%
1809
16th to endDay
20%10%23%26%14%4
2226
April1st to 15thDay
26%9%16%26%16%5%
2149
16th to endDay
21%6%17%28%19%5%
2160
May1st to 15thDay
21%5%12%31%23%4
2291
16th to endDay
32%6%10%21%23%6%
2586
June1st to 15thDay
23%6%8%20%28%12%
2520
16th to endDay
13%3211%36%31%
2520
July1st to 15thDay
21%347%20%41%
2371
16th to endDay
24%448%16%41%
2459
August1st to 15thDay
19%3311%18%43%
2198
16th to endDay
17%229%33%34%
2292
September1st to 15thDay
20%2311%29%32%
2160
16th to endDay
14%2424%33%19%
1998
October1st to 15thDay
19%46%24%29%15%
1765
16th to endDay
15%48%24%34%12%
1720
November1st to 15thDay
18%6%11%30%24%9%
1584
16th to endDay
14%7%15%26%30%6%
1620
December1st to 15thDay
19%9%17%29%18%4
1467
16th to endDay
23%13%16%20%20%5%
1536
January1st to 15thNight
20%6%17%25%23%6%
2506
16th to endNight
21%9%15%21%21%11%
2532
February1st to 15thNight
21%6%14%29%18%9%
2181
16th to endNight
21%7%16%30%20%4
1895
March1st to 15thNight
18%7%20%24%21%8%
2150
16th to endNight
19%8%21%28%17%3
1998
April1st to 15thNight
22%8%16%29%19%3
1799
16th to endNight
19%6%17%31%21%4
1800
May1st to 15thNight
18%5%13%31%25%5%
1659
16th to endNight
21%5%12%27%26%6%
1528
June1st to 15thNight
17%410%24%31%11%
1440
16th to endNight
8%2317%36%31%
1440
July1st to 15thNight
9%35%11%30%40%
1360
16th to endNight
17%4212%24%38%
1444
August1st to 15thNight
11%3315%23%42%
1737
16th to endNight
9%3313%39%30%
1910
September1st to 15thNight
9%3415%38%29%
1800
16th to endNight
12%35%22%37%19%
1962
October1st to 15thNight
16%46%28%33%9%
1989
16th to endNight
13%310%26%36%10%
2150
November1st to 15thNight
14%8%11%30%24%10%
2275
16th to endNight
14%5%13%27%31%7%
2340
December1st to 15thNight
19%10%19%24%22%3
2490
16th to endNight
22%12%15%22%20%6%
2688

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
18%15%35%16%10%5%
60
16th to endDay
9%14%26%28%14%6%
219
February1st to 15thDay
6%14%28%27%20%3
255
16th to endDay
318%33%28%13%1
238
March1st to 15thDay
7%17%31%21%15%6%
270
16th to endDay
6%29%30%23%8%
288
April1st to 15thDay
11%30%26%20%8%2
269
16th to endDay
13%30%30%17%5%2
270
May1st to 15thDay
14%22%36%15%7%3
288
16th to endDay
16%22%23%20%13%3
330
June1st to 15thDay
12%25%28%21%8%2
315
16th to endDay
318%36%24%13%3
315
July1st to 15thDay
9%11%28%29%17%3
305
16th to endDay
10%11%25%36%11%4
327
August1st to 15thDay
7%14%32%26%15%3
315
16th to endDay
6%8%32%30%16%4
332
September1st to 15thDay
9%10%29%33%13%3
315
16th to endDay
6%17%21%35%16%1
315
October1st to 15thDay
12%20%32%21%10%3
278
16th to endDay
9%18%33%28%10%
232
November1st to 15thDay
113%13%24%30%17%
90
16th to endDay
7%22%20%26%20%3
90
December1st to 15thDay
15%15%40%20%7%1
65
16th to endDay
6%9%20%39%18%6%
64
January1st to 15thNight
37%24%31%21%11%
720
16th to endNight
5%427%34%17%11%
768
February1st to 15thNight
36%27%32%21%8%
704
16th to endNight
48%29%33%16%6%
632
March1st to 15thNight
36%32%30%18%8%
720
16th to endNight
311%33%29%17%4
768
April1st to 15thNight
5%10%28%34%16%3
719
16th to endNight
5%11%25%30%18%7%
720
May1st to 15thNight
5%7%29%31%21%5%
579
16th to endNight
7%6%20%31%29%5%
406
June1st to 15thNight
6%421%38%26%3
360
16th to endNight
217%50%24%5%
360
July1st to 15thNight
215%48%37%4
340
16th to endNight
28%43%37%7%
406
August1st to 15thNight
1212%40%36%7%
663
16th to endNight
2111%37%39%7%
764
September1st to 15thNight
1212%34%40%8%
720
16th to endNight
3416%32%31%11%
716
October1st to 15thNight
45%19%34%26%9%
684
16th to endNight
36%17%32%26%13%
704
November1st to 15thNight
2424%33%26%9%
700
16th to endNight
39%25%30%22%8%
720
December1st to 15thNight
37%30%34%16%7%
720
16th to endNight
29%34%32%16%4
768
Page generated at 2017-10-07 11:07:53. Version ac04

Copyright 2017 A. Danko


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